300hp 307

88hurstolds said:

Not sure what this has to do with this thread....

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Has to do with what Maryland G-man said in post #93, the post you were replying to:

Maryland G-man said:

He knows what he is talking about, technically, or at least WAYYY more than I do.

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MadDrOlds said:

Call it a thought experiment:

Lets say we wanted 300 hp out of a 307 vin 9 that would pass a tailpipe emissions test (forget about California).

Pretend we have an unlimited budget (I don’t, but we’re pretending).

Further assume we want a generally stock and 80s period correct appearance (so, no highrise through the hood, no ls fuel injection.

How would you do it?

PS-Lets go ahead and stipulate 1). This is crazy! 2) it costs too much! 3) chevy is cheaper! 3) LS is more reliable! Etc etc etc.

Can it be done, and how?

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300+ hp is achievable with the Olds 307. I have had in depth discussions with several engine builders, who are experienced with the Olds engine. Here is what is needed:

Full rebuild, boring out the cylinders slightly (a few extra cubic inches)
Bump up compression ratio to 9.5:1
Port and polish cylinder heads
Hotter camshaft
Extrusion hone Aluminum intake manifold, and Exhaust Manifolds
Performance rebuild of the Quadrajet Carburetor
True dual exhaust

I plan to do this in early 2026 in my 1984 Hurst/Olds. I want to keep it as stock looking as possible, with the numbers matching engine. I will keep the stock Air Pump, Air Injection, and Chrome Air Cleaner system. I will get it dyno-ed, and provide that data to this forum.

Although the current Mondello company suffers from some concerns to its reputation, please peruse the attached article.

Will be a good build to watch.

There has been 450HP out the 307, Dale Robinson did it. It means moving ports around in the head, high compression, better ring packs etc. An aggressive cam, headers and dual exhaust. Forget more than 250HP with the terrible Vin 9 exhaust set up.

I just went through the read on Dale Robinson build. Big issue will be finding a 330 forged crank. I have one or at least still should have. After the theft of the shop in 2018, I think I still have the crank, more than willing to donate to the build, will just have to look. Hopefully still there.

The other issue is he metal sprayed the heads to work on the exhaust ports. This might be out of range for most builders. And he had custom pistons made. On the cam he was about 240 duration, but raised everything to about .600-ish lift.

Typically and just like the Chevy, going over .500 lift needs modification. I always found it best to stay around 235 - 245 duration and .480 - .530 lift. This keeps major mods to heads at a minimum. On a street budget build, is reason I like the .488 lift, 240ish duration. With stock, and even 305HO heads, works just fine, and even better with aluminum aftermarket with 1.6 exhaust.

On the Olds 307, I can see where aftermarket aluminum heads could work if it keeps CR 10:1 or so and allow for .550 lift, beehive springs. If this can work, then this could develop a parts package, to make a build like this repeatable and reproducible. I've built several Olds over the years and always a disappointment to the lack of 307 support.